Combined process for manufacturing enriched water-gas and aromatic hydrocarbons



May 7, 1957 G. R. BENZ A "2,791,548 C COMBINED PROCRss- FORMANUFACTURING ENRxCx-IEO RATER-CAS AND AROMATIC HYOROCARBONS Filed Jan.3, 1952 ATTORNEYS l United States Patent O COMBINED PROCESS FORMANUFACTURING ENRICHED WATER-GAS AND AROMATIC HYDROCARBONS George R.Benz, Bartlesville, Okla., assigner' to Phillips Petroleum Company, acorporation of Delaware Application January 3, 1952, Serial No. 264,739

5 Claims. (Cl. 19d-55) The invention described herein pertains to aprocess for manufacturing enriched water-gas and aromatic hydrocarbons.The process utilizes pebble heater type apparatus to effect a water-gasreaction and a combination quench-cracking chamber to produce aromatichydrocarbons from atomized heavy hydrocarbon oil.

Pebble heat-exchange apparatus has been applied to a wide variety ofprocesses where rapid heating of gases to high temperatures isdesirable, including heating of air, nitrogen, steam, and gaseousreactants. In this type of operation, a continuous compact mass ofhighly refractory pebbles descends by gravity through a series ofheat-exchange chambers, absorbing heat from a hot gas, usuallycombustion gas, in an upper chamber and delivering the heat required forheating and/or chemical reaction in a lower chamber by direct contactwith the feed gas therein.

The pebbles utilized in the process may be any of the conventionalpebbles of the art. The term pebble as used throughout thisspecification denotes any solid refractory contact material, eithercatalytic or non-catalytic uniform in size in a given process, but maybe of other -L shapes, either regular or irregular and non-uniform insize. Spheres of about 1A; inch to l inch in diameter function desirablyin pebble heat-exchange processes and those in the range of 1A inch toVs inch are most practical. Since pebble heat-exchange apparatus has itsgreatest utility in processes requiring gas heating and/ or reactiontemperatures upwards of about l500 F., pebbles must be formed ofmaterial that will withstand extremely high temperatures. In somehydrocarbon cracking processes, pebbles must withstand temperatures of3000 F. or even higher. Serviceable heat and abrasive resistant pebbleshave been compacted from alumina, mullite, alumina-mullite, zirconia,magnesia, beryllia, thoria, periclase, natural and synthetic clays, andmixtures of these materials. SpheresV formed of high temperature alloysand metals have also beenfound prac-g tical in some processes.

One ofthe problems of the petroleum industry is the utilization ofVheavy hydrocarbon oils such as heavy fuel oils and residualhydrocarbons lfrom various refinery processes conventionally termedheavy residuum. Due to the abundance of this type of hydrocarbon and therelatively small demand for the same, it is desirable to convert as muchas possible into lighter, more valuable hydrocarbons by cracking, butcracking such material to produce Ylighter hydrocarbons involvesdiiculties which have ,been hard to overcome. The process of thisinventionoffers a simple and effective method of cracking heavyhydrocarbons to lighter hydrocarbons, particularly normally gaseoushydrocarbons and aromatics.

The water-gas reaction has` long been used to produce large quantitiesof CO and H2 which can be effectively ICC utilized as fuel or assynthesis gas for the synthesis of hydrocarbons useful as motor fuel. Inmany instances it is desirable to up-grade the water-gas so as toincrease the B. t. u. content of the same and render it more valuable asa fuel gas. TheV present invention provides a process which effectivelyproduces an enriched water-gas and simultaneously produces valuablearomatic hydrocarbons.

The principal objective of the invention is to provide an improvedprocess for producing an enriched watergas. It is also an object of theinvention to provide a combined process for producing enriched water-gaswhile simultaneously producing valuable aromatic hydrocarbons fromrelatively inexpensive raw material. Another object of the invention isto afford better utilization of heat and greater efiiciency in a processfor producing enriched water-gas. Other objects of the invention willbecome apparent from a consideration of the disclosure.

The invention entails the reaction in a pebble heater reactor of amixture of steam and hydrocarbon in vapor form under water-gas producingconditions, whereby an eiiluent containing large proportions of CO andH2 at a temperature in the range of 1700 to 2500 F. is produced andimmediately quenched with atomized heavy hydrocarbon oil in acombination quench-cracking chamber which is maintained under conditionseffective in cracking the atomized oil to hydrogen, light olefins, andaromatic hydrocarbons ranging from benzene to naphthalene and heavier.The gaseous eluent from the quench-cracking chamber containing thewater-gas and hydrocarbons produced from the cracking of the heavy oilboiling below the temperature maintained in the quench-cracking chamberis separated into a normally gaseous fraction comprising the enrichedwater-gas and a normally liquid fraction comprising principally thearomatic hydrocarbons. The normally liquid fraction from the crackingstep is then fractionated to recover the lighter aromatics boiling belowabout 400 F. leaving a bottoms fraction containing heavier aromaticssuch as naphthalene, heavier alkalated benzenes, `and other heavyhydrocarbons. This heavy fraction is then utilized as fuel for supplyingthe hot combustion gas required for heating the pebbles in the pebbleheating chamber as taken from the fractionator or after passing througha naphthalene recovery system where the naphthalene is extracted as aproduct of the process. The bottoms from the oil cracking step may becombined with the bottoms from the fractionator ybefore or afternaphthalene recovery from the fractionator bottoms.

For a more complete understanding of the invention reference may be hadto the drawing which shows a diagrammatic arrangement of apparatusparticularlyV adapted for effecting the process of the invention. Thedrawing shows a typical pebble heater apparatus comprising a pebbleheater chamber 11 and a reactionrchamber 12 connected by throat 13 soasto provide for gravitation of the pebbles in a compact mass from thepebble inlet in the heater to the pebble outlet in the reactor. A pebblechute 14 connected with the pebble outlet of Yreactor 12 carries pebblesby gravity flow to the bottom of elevator 16 which may be of the buckettype or of any other conventional lifting type of device suitable fortransferring pebbles from chute V14 to chute 17 from which the pebblesflow by gravity into the top of heater 11. The llow of pebbles throughthe heater and reactor is controlled by a pebble feeding device, notshown, in chute 14.

ln processing hydrocarbons, suitable fuel is burned in the lower sectionof heater l1 or in an adjacent burner and the hot combustion gas ispassed upwardly through the void spaces between the pebbles and is takenolf through stack 21. In the process of the invention the principal orsole source of fuel is the heavy bottoms product from the cracking ofthe heavy hydrocarbon used in quenching the hot etlluent from reactor12. Auxiliary fuelgline 19 is used to provide light liquid or gaseousfuels to supplement the heavy fuel in line 18, where desired ornecessary to expedite the burning of the heavy fuel. The pebbles inheater 11 are heated to a temperature of at 'least V100 F. above thedesired reaction temperature to be maintained in reactor 12 which is inthe range of 1700 to 2500", thereby requiring an entrance pebbletempera` ture in the range 1800 to 2600 and higher, dependingprincipally upon pebble and feed ow rates. The hot 'pebbles in reactor12 are contacted with a mixture of hydrocarbon in vapor form and steamintroduced to the bottom of the reactor through line 22, the steam beingintroduced to line 22 through line 23. As the hydrocarbon-'steam mixturepasses upwardly through reactor 12 the temperature of the gas is rapidlyincreased to reaction temperature,v and water-gas comprising CO and Hzis formed in the upper section of the reactor. The hot efhuent taken olthrough line 24 is passed through line 27, which may be an' expandedconduit, in admixture with atomized heavy fuel oil or' `other heavyhydrocarbon mixture introduced through line 26. The amount of atomizedfuel oil is regulated in proportion to the amount and Vtemperature ofthe effluent passing through line 24 so as to maintain a temperature inquench-cracking chamber 28 in the range of 1000 to 1400 and effectivelycrack the atomized oil to hydrogen and lighter hydrocarbons comprisingolens and aromatics. Uncracked and other hydrocarbons boiling above thetemperature maintained in quench-cracking chamber 28 collect in the`bottom of the chamber while the vaporized fraction including thewater-gas and lighter products of the crackedquench oil pass throughline 29 to quench chamber 31 Where this stream is quenched with waterspray admitted through line 32 to a temperature inthe range 300 to 400F., preferably about 300 F. This quench knocks out the aromatics andother hydrocarbon oils boiling above the quench temperature and theseare withdrawn through line 34 and processed as hereinafter set forth.The gaseous efuent from quench tank 31, including the H2O together Awiththe enriched Water-gas, is passed through line 33 to quench tank 36where practically all of the Water and products boiling aboveapproximately 100 F. are knocked out. The gaseous efuent from quenchtank 36 passes out through line 38 as the enriched water-gas product ofthe process and may be further dried or processed in any other desirablemanner preparatory to using the same as fuel in a city gas system orother application. The condensate from quench tank 36 is passedthroughline 39 to a phase separator 41 from which the hydrocarbons areWithdrawn -through line 42 and passed to fractionating tower 44. Waterintroduced to the process in the pebble heater reactor through line 23and through lines 32 and 37 to the quench tanks, settles to the bottomof phase separator 41 and is withdrawn through line 43 for disposal orrecycling as quench Water or steam.

The liquid bottoms from quench tank 31, containing principally theolei'lns, aromatics, and other'hydrocarbons boiling between atemperature in the range of 300 to 400 F. is passed through line 34 to afractionator or other separation means 46, in which the lighter morevaluable aromatics, such as those boiling below about 400 F., are ltakenoff overhead through line 47 and passed to fractionator 44 forseparation together with the eluent from line 42 into various aromaticproducts such as benzene, toluene, and xylene for recovery through lines49, 51, and 52, respectively. The higher boiling aromatics and otherhydrocarbons in the overhead from fractionator 46 and phase separation41 are recovered through line 53.

The liquid bottoms from fractionator 46, including heavy aromatics suchas naphthalene, are withdrawn through line 54 and mixed with the liquidbottoms from quench-cracking chamber 23 passing through line 56 and theadmixture is passed through line 57 either directly to pebble heaterfuel line 181er indirectly thereto through line 59, naphthalene recoverysystem 61, and effluent line 62. Naphthalene recovery system 61 may beof any conventional type or design from which the naphthalene isrecovered through line 63.-

It is desirable in some instances to pass the-heavy liquid product fromquench-cracking zone 2S through line 64 directly to fuel line 18 Withoutmixing this fuel with the bottoms product from fractionator 46 prior tothe recovery of naphthalene from the material in line 37. It is, ofcourse, feasible to utilize the heavy hydrocarbon in line 64 as the Solesource of fuel where its, quantity is sufficient. In this casetheresidual hydrocarbon from the naphthaleue recovery can be Withdrawnthrough line 66 for any suitable use or process.

The hydrocarbon raw material for the Water-gas may comprise anyhydrocarbon in vapor form but is preferably made-up of normally gaseoushydrocarbons and particularly propane. The hydrocarbon feed is mixedwith steam in a ratio of hydrocarbon to steam in the range of 1:l to1:10 and the reaction temperature is main tained in the range of 1700 to2500 F. and preferably above 2000 F. in order to produce maximumquantities of CO and H2 and also to provide the maximum amount of heatfor cracking the oil atomized into the hot watergas effluent. It hasbeen found that 87 lbs. of heavy oil can be cracked for each lbs. ofhydrocarbon feed passed into the pebble heater reactor. The amount ofatomized oil mixed or sprayed into the hot water-gas stream and reactedin the quench-cracking chamber is regulated so as to maintain asuita'ble temperature Within the range of 1000 to 1400o F. andpreferably at least 1100 F. so as to produce maximum amounts ofaromatics in the cracking step.

When converting propane and steam to water-gas without the use of an`oil quench for enriching the watergas, for each hundred pounds ofpropane fed to the process there is produced 8,462 ft.3 of water-gashaving a B. t. u. value of B10/ft.3 land a specific gravity of 0.343 ascompared with the process of the invention in which approximately 87lbs. of oil is cracked for each hundred lbs. of propane feed and thereis produced 9,177 ft.3 of enriched gas having a B. t. u. value of 390/ft.3 and a specifc gravity of 0.380. This comparison which shows avaluable up-grading of the gas and greater yield thereof from a givenamount of propane feed, is based upon a reaction temperature of 2500 F.in the pebble heater, a quench-cracking temperature of 1100 F., a heavyfuel oil-quench oil, and a ratio of 100 lbs. of propane to 163.6 lbs. ofsteam.

Of the 87 lbs. of oil cracked per hundred pounds of propane, 19.5 lbs.of gas of the composition shown in Table I is produced.

Table l Mol percent H2 17.9 C1 27.3 C2 38.8 C3 10.8 C4 5.2

cracked comprises aromatics and vother hydrocarbons boiling in the rangeof 400 to 900 F. The balance of the liquid fraction comprises heavierhydrocarbons and coke.

The hot gaseous effluent from the quench-cracking chamber iswater-quenched to approximately 300 F. so as to knock out the oilwithout condensing any appreciable amount of water and thereby avoidingthe formation of oil emulsions which are `difcult to break. rl`hi'ssimplifies the separation of the liquid stream from the first quenchcomprising the aromatics boiling above 300 F. and allows the gaseousoverhead from the first quench to be water quenched so as to condensethe water entrained in the product stream. This procedure makes itrelatively simple to separate the light aromatics from the Watercondensed in the second quench by passing the mixture to a phaseseparator where the hydrocarbon phase separates from the water phase andis drawn off the top or upper section of the phase separator forseparation in fractionator 44. into its various constituents togetherwith the overhead from the heavier aromatic separation in fractionator46.

it should be evident from the disclosure that the process described isparticularly effective in eliiciently producing an enriched water-gas inmaximum amounts with extremely high utilization of heat and improvedefficiency. The quenching of the water-gas effluent from the pebbleheater reactor with a heavy fuel oil or residuum utilizes the sensibleheat of that stream in a highly eflicient manner by heating and crackingthe heavy hydrocarbon to more valuable products which are recovered inthe process as aromatic hydrocarbons and as light fuel gases in theenriched water-gas product. ln addition, the practically valueless heavyhydrocarbon residuum from the process is utilized in tr e heating of thepebbles in the pebble heater so as to reduce fuel costs and thereby aidin the economics of the process. As further evidence of the eflicientheat utilization of the process it should be noted that a substantialportion of the sensible heat of the waefrluent from the pebble heater isimparted to the heavy residual hydrocarbon from the cracking step andfrom fractionator 46, and this heavy hydrocarbon is passed in hotcondition to the pebble heater as fuel, thereby utilizing its sensibleheat in producing higher temperatures in the pebble heating chamber thanwould be produced with the same amount of cold fuel. It should also benoted that the quenching and cracking of heavy oil utilizes valuableheat of the effluent water-gas to simultaneously enrich the water gasand produce valuable aromatic hydrocarbons.

Cert-ain modifications of the invention will become apparent to thoseskilled in the art yand the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

l claim:

1. A continuous process for cracking hydrocarbon to produce enrichedWater-glas and aromatic hydrocarbons which comprises heating agravitating compact mass of pebbles in a heating zone to a temperatureat least 100 F, above the hereinafter specified reaction temperature;contacting the resulting gravitating hot stream of pebbles in a reactionzone with a gaseous stream comprising hydrocarbon and steam in a weightratio of hydrocarbon to steam in the range of 1:1 to 1:10 at a reactiontemperature in the range of 1700 to 2500 F. so as to produce water-gas;passing the water-gas-containing effluent into a combinationquench-cracking zone and quenching same with a heavy liquid hydrocarbonhaving an initial boiling point above 600 F. in such an amount as tomaintain a cracking temperature in the range of 1000 to 1400 F. therebyvaporizing and cracking a substantial portion of said liquid hydrocarbonto H2 and lighter hydrocarbons including aromatics solely by thesensible heat of said eflluent; separating the gaseous effluent fromsaid quenchcracking zone into a normally gaseous fraction comprisingwater-gas enriched with H2 and normally gaseous hydrocarbons produced inthe quench cracking step and a heavier fraction comprising aromatichydrocarbons by first water-quenching said effluent to a temperature inthe range of 300 to 400 F. and then water-quenchingthe remaining gaseouseffluent to knock out light liquid hydrocarbons and Water therefrom;fractionating said heavier fraction so as to recover an Overheadfraction boiling below a temperature in Ithe range of 350 to 400 F.containing aromatic hydrooarbons and a bottoms fraction containingnaphthalene; recovering naphthalene from said bottoms fraction to form aresidual bottoms fraction; recovering a liquid fraction from saidquench-cracking zone and combining same with said residual bottomsfraction to form a mixed heavy hydrocarbon fraction; burning at least aportion of said combined heavy hydrocarbon fraction in said heating zoneto heat s-aid pebbles; and recycling pebbles from said reaction zone tosaid heating zone for reheating.

2. The process of claim 1 in which the hydrocarbon feed to said reactionzone is a propane-rich gas.

3. A continuous process for cracking hydrocarbons to produce enrichedwater-gas and varomatic hydrocarbons which comprises heating agravitating compact mass of pebbles lin a pebble heating zone to atemperature at least F. above the hereinafter specified reactionternperature; contacting the resulting gravitating hot stream of pebblesin a reaction zone with a mixture of propane and steam in a weight ratioof hydrocarbon to steam in a range of 1:1 to 1:10 at a reactiontemperature in the range of 2000 to 2500 F. so as to produce water-gas;passing the water-gas containing efuent into a combinationquench-cracking zone and quenching same with a heavy liquid hydrocarbonhaving an initial boiling point above 600 F. in such an amount as tomaintain a cracking temperature of 1100 to 1400 F. thereby vaporizingand cracking a substantial portion of said liquid hydrocarbon to H2 andlighter hydrocarbons including aromatics solely by the sensible heat ofsaid efiiuent; passing the gaseous effluent from said quench-crackingzone into a first water-quench zone and quenching the eiiiuent to atemperature of 300 F. so as to knock out the hydrocarbon oil boilingabove said temperature while passing the uncondensed fraction comprisingsteam and hydrocarbons boiling below said temperature to a secondwater-quench zone; water-quenching said uncondensed fraction in saidsecond water-quenching zone to a temperature of 100 F. so as to recovera gaseous effluent therefrom containing enriched water-gas and acondensate containing essentially all of the H2O and hydrocarbonsboiling in the range of 100 to 300 F.; separating said condensate byphase separation into a hydrocarbon fraction and a water fraction;passing said hydrocarbon fraction comprising principally aromatichydrocarbons, into a irst fraotionating zone together with a secondaromatic fraction derived as hereinafter described and separating acombined aromatic feed into separate fractions consisting essentially ofbenzene, toluene, aud xylenes, respectively; passing the condensate fromsaid first water-quenching zone to a second fractionating zone andseparating same into an aromatic overhead fraction boiling below 400 F.and bottoms fraction including naphthalene; passing said overheadaromatic fraction to said first fractionator; recovering naphthalenefrom said last-named bottoms fraction and burning the residualhydrocarbon therefrom in admixture with the bottoms from saidquench-cracking zone in said pebble heating zone so as to heat saidpebbles; and recycling pebbles from said reaction zone to said heatingzone for reheating.

4. A continuous process for cracking hydrocarbon to produce enrichedWater-gas and aromatic hydrocarbons which comprises heating agravit-ating compact mass of pebbles in a heating zone to a temperatureat least 100 F. above the hereinafter specified reaction temperature;contacting the resulting gravitating hot stream of pebbles in a reactionzone with a gaseous stream comprising hy- 7 drocarbon and steam in aweight ratio of hydrocarbon to steam in the range of 1:1 to 1:10 at areaction temperature in the range of 1700 to 2500" F. so `as to producewater-gas; passing the water-gas containing eluent into a combinationquench-cracking zone and quenching same with a heavy liquid hydrocarbonhaving an initial boiling point above 600 F. in such an amount as tomaintain a cracking temperature in the range of 1000 to 1400 F. therebyvaporizing and cracking a substantial portion of said liquid hydrocarbonto H2 and lighter hydrocarbons including aromatics solely by thesensible heat of said eluent; passing the gaseous elluent from saidquench-cracking Zone into a first Water-quench zone and quenching theetiiuent to ya temperature in the range of 300 to 400 F. so as to knockout hydrocarbon oil boiling above said .temperature while passing theuncondensed fraction comprising steam and hydrocarbons boiling belowsaid temperature to 'a second water-quench zone; water-quenching saiduncondensed fraction in said second water-quenching zone to Aatemperature of about 100 F. so as to recover a gaseous effluenttherefrom containing enriched water-gas and a condensate containingessentially all of the H2O and hydrocarbons boiling in the range of 100to 300n F.; passing said hydrocarbon fraction comprising aromatichydrocarbons, into a iirst fractionating zone together with a secondaromatic fraction derived as hereinafter described and recoveringtherefrom benzene, toluene and Xylenes; passing the condensate from saidfirst Water-quenching zone to a second fractionating zone and separatingsame into an aromatic overhead fraction boiling below 400 F. and abottoms fraction including naphthalene; passing said overhead aromaticfraction to said rst fraetionator; recovering naphthalene from saidlast-named bottoms fraction and burning residual hydrocarbon therefromin admixture with the bottoms from said quench-cracking zone in saidpebble beating zone so as to heat said pebbles; and recycling pebblesfrom said reaction zone to said heating zone for reheating.

5. The process of claim 4 including the step of separating by phaseseparation the condensate from said second Water-quenching zone into ahydrocarbon fraction and a water fraction.

References Cited in the lile of this patent UNITED STATES PATENTS1,972,833 Subkow Sept. 4, 1934 2,016,798 Cooke Oct. 8, 1935 2,431,515Shepardson Nov. 25, 1947 2,544,188 Steinschlaeger Mar. 6, 1951 2,555,210Waddill et al. May 29, 1951 2,605,215 Coghlan Iuly 29, 1952 2,608,478Pollock Aug. 26, 1952 2,616,678 Grossman Nov. 4, 1952 OTHER REFERENCESSachanen: Chemical Constituents of Petroleum (1945), pages 273-275;Reinhold, N. Y. publishers.

1. A CONTINUOUS PROCESS FOR CRACKING HYDROCARBON TO PRODUCE ENRICHEDWATER-GAS AND AROMATIC HYDROCARBONS WHICH COMPRISES HEATING AGRAVITATING COMPACT MASS OF PEBBLES IN A HEATING ZONE TO A TEMPERATUREAT LEAST 100* F. ABOVE THE HEREINAFTER SPECIFIED REACTION TEMPERATURE;CONTACTING THE RESULTING GRAVITATING HOT STREAM OF PEBBLES IN A REACTIONZONE WITH A GASEOUS STREAM COMPRISING HYDROCARBON AND STREAM IN A WEIGHTRATIO OF HYDROCARBON TO STEAM IN THE RANGE OF 1:1 TO 1:10 AT A REACTIONTEMPERATURE IN THE RANGE OF 1700 TO 2500*F. SO AS TO PRODUCE WATER-GAS;PASSING THE WATER-GAS-CONTAINING EFFLUENT INTO A COMBINATIONQUENCH-CRACKING ZONE AND QUENCHING SAME WITH A HEAVY LIQUID HYDROCARBONHAVING AN INITIAL BOILING POINT ABOVE 600*F. IN SUCH AN AMOUNT AS TOMAINTAIN A CRACKING TEMPERATURE IN THE RANGE OF 1000 TO 1400*F. THEREBYVAPORIZING AND CRACKING A SUBSTANTIAL PORTION OF SAID LIQUID HYDROCARBONTO H2 AND LIGHTER HYDROCARBON INCLUDING AROMATICS SOLELY BY THE SENSIBLEHEAT OF SAID EFFLUENT; SEPARATING THE GASEOUS EFFLUENT FROM SAIDQUENCHCRACKING ZONE INTO A NORMALLY GASEOUS FRACTION COMPRISINGWATER-GAS ENRICHED WITH H2 AND NORMALLY GASEOUS HYDROCARBONS PRODUCED INTHE QUENCH CRACKING STEP AND A HEAVIER FRACTION COMPRISING AROMATICHYDROCARBONS BY FIRST WATER-QUENCHING SAID EFFLUENT TO A TEMPERATURE INTHE RANGE OF 300 TO 400*F. AND THEN WATER-QUENCHING THE RE-